// Copyright 2019 The Gitea Authors. All rights reserved.// SPDX-License-Identifier: MIT package log import (	"bytes"	"fmt"	"os"	"runtime") var unknown = []byte("???") // Stack will skip back the provided number of frames and return a stack trace with source code.// Although we could just use debug.Stack(), this routine will return the source code and// skip back the provided number of frames - i.e. allowing us to ignore preceding function calls.// A skip of 0 returns the stack trace for the calling function, not including this call.// If the problem is a lack of memory of course all this is not going to work...func Stack(skip int) string {	buf := new(bytes.Buffer) 	// Store the last file we opened as its probable that the preceding stack frame	// will be in the same file	var lines [][]byte	var lastFilename string	for i := skip + 1; ; i++ { // Skip over frames		programCounter, filename, lineNumber, ok := runtime.Caller(i)		// If we can't retrieve the information break - basically we're into go internals at this point.		if !ok {			break		} 		// Print equivalent of debug.Stack()		_, _ = fmt.Fprintf(buf, "\t%s:%d (0x%x)\n", filename, lineNumber, programCounter)		// Now try to print the offending line		if filename != lastFilename {			data, err := os.ReadFile(filename)			if err != nil {				// can't read this source file				// likely we don't have the sourcecode available				continue			}			lines = bytes.Split(data, []byte{'\n'})			lastFilename = filename		}		_, _ = fmt.Fprintf(buf, "\t\t%s: %s\n", functionName(programCounter), source(lines, lineNumber))	}	return buf.String()} // functionName converts the provided programCounter into a function namefunc functionName(programCounter uintptr) []byte {	function := runtime.FuncForPC(programCounter)	if function == nil {		return unknown	}	name := []byte(function.Name()) 	// Because we provide the filename we can drop the preceding package name.	if lastslash := bytes.LastIndex(name, []byte("/")); lastslash >= 0 {		name = name[lastslash+1:]	}	// And the current package name.	if period := bytes.Index(name, []byte(".")); period >= 0 {		name = name[period+1:]	}	// And we should just replace the interpunct with a dot	name = bytes.ReplaceAll(name, []byte("·"), []byte("."))	return name} // source returns a space-trimmed slice of the n'th line.func source(lines [][]byte, n int) []byte {	n-- // in stack trace, lines are 1-indexed but our array is 0-indexed	if n < 0 || n >= len(lines) {		return unknown	}	return bytes.TrimSpace(lines[n])}